As diseases such as bovine spongiform encephalopathy, which are fatal to humans, have been determined to be due to animal protein ingredients which are added to animal feed, there has been a rapid worldwide movement to replace animal protein with vegetable protein. A typical example of such a vegetable protein can include a soybean meal. Soybean meal refers to shell components defatted from soybeans. Generally, it is known that soybean meal contains 9.5% of water, 49.4% of crude protein, 22.1% of inverted sugar, and 27.2% of water-soluble nitrogen. However, soybean meal shows substantially the same disadvantages as most vegetable proteins. Specifically, soybean meal has a relatively low protein content in comparison to animal protein, the composition of essential amino acids needed for livestock is insufficient to that of animal protein, and the content of some vitamins, minerals and UGF (Unknown Growth Factor) is not excellent. Further, it contains several anti-nutritional factors (ANF) and so digestibility is inhibited when used in the feedstuff. In particular, anti-nutritional factors such as a trypsin inhibitor, exhibit the effects of inhibiting growth by lowering digestibility of young livestock. Therefore, the amount of soybean meal added to the feedstuff for young livestock is currently limited.
Various studies attempting to solve the above-described problems of soybean meal have been carried out. A variety of products have been developed where the problems of soybean meal have been resolved, for example, a concentrated soybean protein, a purified soybean protein, a fermented soybean meal and the like. However, the concentrated soybean protein and the purified soybean protein are difficult to use for the feedstuff due to their high production costs. As such, the fermented soybean meal is used as the feedstuff. The fermented soybean meal is produced by the fermentation of soybean meal. Soybean meal has advantages in that an animal protein is added in the fermentation process, the content of the above-mentioned anti-nutritional factor is significantly reduced and further proteins or carbohydrates are enzyme-decomposable, thus making a form which is easily digestible by enzymes. Accordingly, soybean meal is widely used as the feed material and the feed additive.
However, in order to produce the fermented soybean meal, a fermentation apparatus for soybean meal must be provided, and excessive fermentation and drying time are necessary, thereby increasing production costs for the fermented soybean meal. Particularly, compared to conventional methods which dry and grind soybean meal and then use it as the feed material or the feed additive, excessive time is spent drying the fermented soybean meal as water is added to soybean meal to maintain a moisture content of from 30 to 80% for fermentation, and additional time is spent fermenting the soybean meal. To overcome this drawback, various studies have been carried out. As a result, techniques capable of producing a fermenting microorganism showing specific effects in fermenting soybean meal and shortening the fermentation time of soybean meal have been developed. For example, Korean Patent Application Publication No. 2011-0027535 discloses a technique to shorten the fermentation time of soybean meal with the Bacillus subtilis TP6 strain.
As such, techniques capable of shortening the fermentation time in the production of the fermented soybean meal have been developed, but techniques to shorten the drying time of fermented soybean meal have not yet been developed.
Using production processes of the fermented soybean meal developed until now, the fermented soybean meal is dried by introducing outside air into the fermentation apparatus immediately after fermentation. The fermentation apparatus contains excessive moisture content in addition to the moisture of the fermented soybean meal and so it takes a long time to remove the moisture. Strategies to shorten the time required for drying the fermented soybean meal by transferring the fermented soybean meal from the fermentation apparatus to a separate drying apparatus and then drying it have been conducted. However, since soybean meal immediately after completion of fermentation contains excessive moisture content, it proved problematic as the soybean meal stuck to the conveyer or transfer channel, blocking the pathway for transfer.
Given these circumstances, the present inventors have conducted numerous and intensive research to develop methods capable of shortening the drying time of the fermented soybean meal during the production of fermented soybean meal. As a result, the inventors have discovered that, when the fermented soybean meal is eddycurrent-transferred while maintaining the moisture content in the fermented soybean meal to 28% or less, the fermented soybean meal can be easily transferred to the drying apparatus and dried in the drying apparatus, thereby shortening the drying time. The present invention has been completed on the basis of this discovery.
The foregoing discussion in this section is to provide general background information, and does not constitute an admission of prior art.